The present invention relates to a power control device utilized in a power semiconductor device.
An output circuit in a driver of such as motor or actuator, a power source circuit, or the like, includes a circuit breaker for cutting off an output current in order to protect circuit elements from excess current or control the output current so as to avoid exceeding a predetermined value.
FIG. 13 shows one conventional example of the circuit breaker. An output transistor 1 is a transistor for driving a load 3. A register 101 for detecting current is connected in series with the output transistor 1. The potential difference across the resistor 101, namely the voltage drop due to the current flowing through the output transistor 1 (hereinafter referred to as output current) is compared with a reference voltage 102 through a differential amplifier 103. The reference voltage 102 is set to be equal to the voltage drop due to a control target amount of the output current. The comparison result of the differential amplifier 103 is outputted to a control circuit. The control circuit cuts off the output transistor 1 when the output current is larger than the control target amount, that is to say, when the output of the differential amplifier 16 is negative. The output transistor 1 which has been once cut off is held under the cutoff condition by the control circuit. The control circuit allows the output transistor 1 to conduct the current again in the case of receiving a signal indicating the directions to conduct the current from the outside or when the output of the differential amplifier 103 becomes positive after a predetermined time has passed. Thus, the output current avoids substantially exceeding the control target amount.
In the above-described conventional example of FIG. 13, however, the resistor 101 is connected in series with the output transistor 1. Therefore, there is the problem of narrowing the range of the output voltage or spending the wasted power.
FIG. 14 shows another conventional example of the circuit breaker. In the conventional example, the above-described problem with the conventional example is solved as follows.
In the second conventional example, an auxiliary transistor 2 is connected in parallel to the output transistor 1 and the current-detecting resistor 101 is connected in series with the auxiliary transistor 2. The current I2 outputted by the auxiliary transistor 2 (hereinafter referred to as adjusting current) is smaller by a predetermined ratio than the output current I1 outputted by the output transistor 1 applied with the common input. For example, in the case where the output transistor 1 and the auxiliary transistor 2 are monolithically formed such as an integrated circuit or the like, the structure of the auxiliary transistor 2 is substantially the same as the output transistor 1 but the size thereof is smaller than the output transistor 1. In that case, the ratio of the currents outputted by the respective transistors applied with the common input voltage substantially equals to the ratio of the sizes of the transistors.
By utilizing the current-detecting resistor 101, the adjusting current I2 is controlled so as not to exceed the control target value in the same way as the first conventional example. When the voltage drop across the resistor 101 is sufficiently small to be ignorable in comparison with the voltage inputted to the output transistor 1, the current ratio I1/I2 is substantially equal to the size ratio of the transistors. After all, the current I1 is proportional to the current I2, and the proportional coefficient is substantially determined by the size ratio of the transistors and substantially independent of the input voltage, the temperature of the environment and the like. Accordingly, the output current I1 can be controlled so as not to exceed an amount larger than the above-described control target amount by the inverse of the above-described ratio. In the second conventional example, since the resistor 101 is not connected in series with the output transistor 1, the range of the output voltage can be widened in comparison with the first conventional example and, at the same time, the wasted power can be reduced.
When the voltage drop across the resistor 101 is large and not ignorable in comparison with the voltage inputted to the output transistor 1, the voltage between gate and source (hereinafter referred to as gate voltage) of the output transistor 1 is larger than the auxiliary transistor 2 by the voltage drop across the resistor 101. Thus, the ratio I1/I2 of the output current I1 to the adjusting current I2 depends on not only the size ratio of transistors but also either of the voltage between source and drain or the gate voltage, and parameters such as the threshold value of the gate voltage. Accordingly, the relation between the output current I1 and the adjusting current I2 is, in general, non-linear. In particular, the output current I1 tends to increase more largely than the adjusting current I2 beyond the ratio determined by the size ratio of the transistors, and the current ratio I1/I2 in the region of the large gate voltage is several times or more larger than the size ratio of the transistors.
FIG. 16A is a diagram showing a graph representing the changes of the output current I1 and the adjusting current I2 with respect to the gate voltage of the output transistor 1 in the second conventional example. Here, the vertical axis of the figure is normalized in order that the difference from the proportionality may be easily seen. In fact, if the curve corresponding to the output current I1 and the curve corresponding to the adjusting current I2 agree with each other, the relation between the output current I1 and the adjusting current I2 is proportional. As shown in FIG. 16A, in the second conventional example, the output current I1 and the adjusting current I2 do not agree particularly in the region of the large gate voltage. In addition, the difference between the above-described two curves changes greatly owing to a change of the threshold value of the gate voltage caused by the temperature. Since the current ratio I1/I2 changes depending on the gate voltage and the temperature in that manner, the output current I1 varies from a predetermined value even if the adjusting current I2 is controlled so as to be set at a predetermined control target value. Therefore, the second conventional example cannot make the control precision of the output current I1 sufficiently high and secure sufficient reliability.
FIG. 15 shows the third conventional example of the circuit breaker. This conventional example has an output transistor 1 and a parallel-connected auxiliary transistor 2 in the same way as the second conventional example. In the third conventional example, the voltages between drain and source are different from each other between the output transistor 1 and the auxiliary transistor 2 in contrast with the second conventional example, though the gate voltages of the transistors are the same. In the output transistor 1 in particular, the voltage between drain and source tends to reduce remarkably owing to a voltage drop across the load 3.
FIG. 16B is a diagram showing a graph representing the changes of the output current I1 and the adjusting current I2 with respect to the gate voltage in the third conventional example. The vertical axis of FIG. 16B is normalized in the same way as FIG. 16A. As shown in FIG. 16B, in the third conventional example, the output current I1 and the adjusting current I2 do not agree when the gate voltage is raised to a certain level. In particular, the output current I1 shows a change to become saturated together with the increase of the gate voltage. Accordingly, the control precision of the output current I1 cannot be made high sufficiently in the third conventional example similar to the second conventional example since the current ratio I1/I2 changes depending on the gate voltage.
The cause of dependence of the ratio I1/I2 of the output current I1 to the adjusting current I2 on a variety of fluctuation factors is the difference between the gate voltages of the output transistor 1 and the auxiliary transistor 2 in the second conventional example, and the difference between the voltages between drain and source thereof in the third conventional example, respectively. Therefore, the present invention provides a power control device for controlling the potentials of the three terminals (gate, source and drain) of the output transistor land the auxiliary transistor 2 so as to equalize the potentials of the corresponding terminals, thereby adjusting the ratio I1/I2 of the output current I1 to the adjusting current I2 to a constant level. Thus, the output control precision is independent of operational conditions, temperature change, or unevenness of the size ratio and the like owing to the varied conditions in the production, thereby improving reliability of the power control device in comparison with the conventional examples.
A power control device according to the present invention comprises:
a bridge circuit consisting of a first branch, a second branch, a third branch and a fourth branch, wherein
each of said first to fourth branches includes a first terminal and a second terminal,
the first terminal of said first branch and the first terminal of said third branch are connected to a first power-source-connecting terminal at a substantially constant potential, the second terminal of said second branch and the second terminal of said fourth branch are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node,
said second branch includes a load,
said first branch includes an output circuit for driving said load, and
said third branch includes an auxiliary circuit for outputting an adjusting current adjusted to an amount smaller substantially by a predetermined ratio than an output current outputted from said output circuit in the case of applying substantially the same input voltage as that of said output circuit;
a potential difference detector for detecting a potential difference between said first node and said second node; and
a control circuit for making said output circuit interlock with said auxiliary circuit, controlling said output circuit and cutting off said output circuit and said auxiliary circuit based on said potential difference detected by said potential difference detector.
Thereby, the output circuit and the auxiliary circuit can be cut off by the control circuit based on the potential difference detected by the potential difference detector, for example, when the difference between the voltages inputted to the output circuit and to the auxiliary circuit exceed a predetermined range. Accordingly, the cutoff level with respect to the difference between the above-described input voltages is set at a corresponding level to the state wherein the ratio of the output current to the adjusting current agrees with the limit of a predetermined tolerance range. As a result, if the above-described ratio exceeds the tolerance range, the power control device can cut off the output.
A power control device according to an aspect, other than the above, of the present invention comprises:
a bridge circuit consisting of a first branch, a second branch, a third branch and a fourth branch, wherein
each of said first to fourth branches includes a first terminal and a second terminal,
the first terminal of said first branch and the first terminal of said third branch are connected to a first power-source-connecting terminal at a substantially constant potential, the second terminal of said second branch and the second terminal of said fourth branch are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node,
said second branch includes a load,
said first branch includes an output circuit for driving said load, and
said third branch includes an auxiliary circuit for outputting an adjusting current adjusted to an amount smaller substantially by a predetermined ratio than an output current outputted from said output circuit in the case of applying substantially the same input voltage as that of said output circuit;
a potential difference detector for detecting a potential difference between said first node and said second node;
a control circuit for making said output circuit interlock with said auxiliary circuit and controlling said output circuit; and
a current ratio compensator for feeding back said detected potential difference detected by said potential difference detector and controlling the equivalent impedance across said first terminal and said second terminal of one of said first to fourth branches so that said bridge circuit keep the balance, thereby holding said ratio at a substantially constant level.
Thereby, the bridge circuit can keep the balance so that the potential difference detected by the potential difference detector, that is to say, the input voltage to the output circuit and the input voltage to the auxiliary circuit become substantially equal. Accordingly, the ratio of the output current to the adjusting current is substantially constant, that is to say, substantially independent of the applied input voltage and the environmental temperature change. Therefore, the control circuit can control the adjusting current with a high precision through the auxiliary circuit, thereby controlling the output current with a high precision in the same way through the interlocking output circuit with the auxiliary transistor. Here, the current ratio compensator controls the equivalent impedance of one element in the bridge circuit, thereby making the bridge circuit keep the balance. Accordingly, xe2x80x9cthe current ratio compensatorxe2x80x9d may be referred to as xe2x80x9cequivalent impedance control circuit.xe2x80x9d
The above-described power control device according to a preferred mode from one aspect has a current detector in said fourth branch for detecting said adjusting current, wherein said control circuit controls said auxiliary circuit based on the detected result of said current detector. When the bridge circuit keeps the balance by the current ratio compensator, the ratio of the output current to the adjusting current is held at a constant level. Accordingly, if the adjusting current is detected with the current detector, the output current can be detected from that result. In that way, the output current can be fed back to the control circuit. In that case, there is no risk in the detecting operation to narrow the possible output range of the output voltage, since the output current need not be measured direct.
According to a preferred mode of the above-described power control device from another aspect, said fourth branch includes a current setting circuit for holding at a substantially constant level or changing quasistatically said adjusting current. If the adjusting current is held constant with the current setting circuit, then the output current is also constant, since the ratio of the output current to the adjusting current is held constant by the current ratio compensator. Alternatively, if the adjusting current changes quasistatically by the current setting circuit, then the output current changes quasistatically in the same manner. Here, quasistatic change means a sufficiently slow change in comparison with the change of the output current and the adjusting current through the output control of the control circuit and the control of the equivalent impedance of the current ratio compensator.
According to a preferred mode of the above-described power control device from still another aspect, said second branch includes a switch circuit connected in series between said load and the second power-source-connecting terminal and for conducting or cutting off said output current based on said potential difference. If the output current changes greatly to lose the balance of the bridge circuit, the switch circuit cuts off the output current in order to prevent an excessive large amount of current of the output current from destroying the elements included in the device and the like. Thereby, the elements of the device and the like are protected from a destructive excess current.
In addition, in that case, the control of said equivalent impedance by said current ratio compensator may be provided over said switch circuit. Thereby, the single switch circuit can be used in order to perform the above-described function as a protective circuit against excess current and the function as a compensator for making the bridge circuit keep the balance.
According to a preferred mode of the above-described power control device from yet another aspect, said current ratio compensator may provide the control of said equivalent impedance over said output circuit. Thereby, the single output circuit can be used in order to perform the original function as a driver for the load, the function as a protective circuit against the above-described excess current and the function as a compensator for making the bridge circuit keep the balance.
A power control device according to one aspect of the present invention, as one of the developments of the above-described power control device, comprises:
an output network consisting of a first branch, a second branch, a third branch, a fourth branch, a fifth branch, a sixth branch and a seventh branch, wherein
each of said first to seventh branches includes a first terminal and a second terminal,
the first terminals of said first, said third and said fifth branches are connected to a first power-source-connecting terminal at a substantially constant potential,
the second terminals of said second, said fourth and said sixth branches are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node, the second terminal of said fifth branch and the first terminal of said sixth branch are mutually connected at a third node,
the first terminal and the second terminal of said seventh branch are connected to said first node and said second node, respectively,
said seventh branch includes a load,
said first branch includes a first output circuit for driving said load,
said third branch includes a second output circuit for driving said load,
each of said second and said fourth branches includes a switch circuit, and
said fifth branch includes an auxiliary circuit for interlocking with either of said first or said second output circuits and outputting adjusting current adjusted to an amount smaller substantially by a predetermined ratio than an output current outputted from the interlocking output circuit in the case of applying substantially the same input voltage as that of the interlocking output circuit;
a potential difference detector for detecting the potential of said first node or said second node with respect to said third node;
a control circuit for making said first and said second output circuits interlock with said auxiliary circuit in a substantially alternate order and controlling said first or said second output circuit;
a switch control circuit for turning on or off said switch circuits in a substantially alternate order in a manner synchronized with the operation of said control circuit; and
a current ratio compensator for feeding back said potential difference detected by said potential difference detector and controlling the equivalent impedance across said first terminal and said second terminal of one of said first to said sixth branches, so that
a bridge consisting of said first branch, a composite of said seventh branch and said fourth branch, said fifth branch, and said sixth branch, keeps the balance when an output current from said first output circuit flows through said first branch, said seventh branch and said fourth branch, and
a bridge consisting of said third branch, a composite of said seventh branch and said second branch, said fifth branch, and said sixth branch, keeps the balance when an output current from said second output circuit flows through said third branch, said seventh branch and said second branch, thereby holding said ratio at a substantially constant level.
The output control device can reverse the output current flowing through the load by turning on or off the two output circuits and the switch circuits in substantially alternate order. The arrangement of only the conducting branches of the output network is substantially the same as the bridge circuit of the above-described power control device and, therefore, the effects thereof are equivalent to the above-described effects.
According to a preferred mode of the power control device from one aspect, said sixth branch includes a current setting circuit for holding at a substantially constant level or changing quasistatically said adjusting current. If the adjusting current is held constant with the current setting circuit, then the output current is constant, since the ratio of the output current to the adjusting current is held constant by the current ratio compensator. Alternatively, if the adjusting current changes quasistatically by the current setting circuit, then the output current changes quasistatically in the same manner.
In the above-described power control device, preferably from another aspect, said current ratio compensator provides the control of said equivalent impedance over said switch circuit. Thereby, the switch circuit for reversing the current flowing through the load can also be used as a compensator for making the bridge circuit keep the balance.
According to a preferred mode of the above-described power control device from still another aspect, said current ratio compensator may provide the control of said equivalent impedance over said first or said second output circuits. Thereby, the same output circuit can be used in order to perform the original function as a driver for the load, the above-described function as a protective circuit against excess current and the function as a compensator for making the bridge circuit keep the balance.
A power control device developed into another mode from the secondarily mentioned power control device according to the present invention comprises:
an output network consisting of a first branch, a second branch, a third branch, a fourth branch, a fifth branch, a sixth branch, a seventh branch, an eighth branch and a ninth branch, wherein
each of said first to ninth branches includes a first terminal and a second terminal,
the first terminals of said first, said third, said fifth and said seventh branches are connected to a first power-source-connecting terminal at a substantially constant potential,
the second terminals of said second, said fourth, said sixth and said eighth branches are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node, the second terminal of said fifth branch and the first terminal of said sixth branch are mutually connected at a third node, the second terminal of said seventh branch and the first terminal of said eighth branch are mutually connected at a fourth node,
the first terminal and the second terminal of said ninth branch are connected to said first node and said second node, respectively,
said ninth branch includes a load,
said first branch includes a first output circuit for driving said load,
said third branch includes a second output circuit for driving said load,
each of said second and said fourth branches includes a switch circuit,
said fifth branch includes a first auxiliary circuit for interlocking with said first output circuit and outputting a first adjusting current adjusted to an amount smaller substantially by a predetermined first ratio than a first output current outputted from said first output circuit in the case of applying substantially the same input voltage as that of said first output circuit, and
said seventh branch includes a second auxiliary circuit for interlocking with said second output circuit and outputting a second adjusting current adjusted to an amount smaller substantially by a predetermined second ratio than a second output current outputted from said second output circuit in the case of applying substantially the same input voltage as that of said second output circuit;
a potential difference detector for detecting the potential of said first node with respect to said third node as a first potential difference and the potential of said second node with respect to said fourth node as a second potential difference;
a control circuit for operating in a substantially alternate order and controlling a pair of said first output circuit and said first auxiliary circuit and a pair of the second output circuit and said second auxiliary circuit;
a switch control circuit for turning on or off one of said switch circuits in a substantially alternate order in a manner synchronized with the operation of said control circuit; and
a current ratio compensator for feeding back said first or said second potential difference detected by said potential difference detector and for controlling the equivalent impedance across said first terminal and said second terminal of one of said first to said eighth branches, so that
a bridge consisting of said first branch, a composite of said seventh branch and said fourth branch, said fifth branch, and said sixth branch, keeps the balance, thereby holding said first ratio at a substantially constant level when said first output current flows through said first branch, said seventh branch and said fourth branch, and
a bridge consisting of said third branch, a composite of said seventh branch and said second branch, said seventh branch, and said eighth branch, keeps the balance, thereby holding said second ratio at a substantially constant level when said second output current flows through said third branch, said seventh branch and said second branch.
The power control device can reverse the output current flowing through the load by turning on or off the two output circuits and the two switch circuits in substantially alternate order in the same manner as described above. The arrangement of only the conducting branches of the output network are substantially the same as the bridge circuit of the secondarily described power control device according to the present invention and, therefore, the effects thereof are equivalent to that secondarily described one.
That power control device, in contrast with the above-described power control device, has two auxiliary circuits one-to-one corresponding to the two output circuits. Thereby, the circuit scale is larger than the above-described power control device. On the contrary, if the ratio of the adjusting current to the output current is set at a predetermined value with a high precision, the above-described power control device requires minimizing the structural difference between the two output circuits since the auxiliary circuit is used in common, but that power control device does not.
In addition, in the case of monolithically forming the power control device according to the present invention as an integrated circuit, the two output circuits must be put apart to a certain extent on the chip in the above-described power control device. Therefore, non-uniformity in position of the temperature or the wafer structure on the chip can easily appear as the difference between the operations of the two output circuits and, as a result, the precision of the output control tends to drop. On the contrary, in that power control device, the output circuit and the auxiliary circuit, both of which correspond to each other, can be formed immediately next to each other and, therefore, the above-described non-uniformity of the temperature or the wafer structure can be substantially ignored for the pair of the circuits.
The above-described power control device according to a preferred mode from one aspect has a current setting circuit for holding at a substantially constant level or changing quasistatically said first adjusting current and said second adjusting current in said sixth branch and said eight branch, respectively. If the adjusting current is held constant with the current setting circuit, then the output current is also constant, since the ratio of the output current to the adjusting current is held constant by the current ratio compensator. Alternatively, if the adjusting current changes quasistatically by the current setting circuit, then the output current changes quasistatically in the same manner.
In the above-described power control device preferably from yet another aspect, said current ratio compensator provides the control of said equivalent impedance over said switch circuits. Thereby, the switch circuit for reversing the current flowing through the load can also be used as the compensator for making the bridge circuit keep the balance.
According to a preferred mode of the above-described power control device from still another aspect, said current ratio compensator may provide the control of said equivalent impedance over said first or said second output circuits. Thereby, the same output circuit can be used in order to perform the original function as a driver for the load, the above-described function as a protective circuit against excess current and the function as a compensator for making the bridge circuit keep the balance.
A power control device according to the present invention, as a development of the secondarily described power control device of the present invention from still another aspect, comprises:
an output network consisting of a first branch, a second branch, a third branch, a fourth branch, a fifth branch, a sixth branch, a seventh branch and an eighth branch, wherein
each of said first to eighth branches includes a first terminal and a second terminal,
the first terminals of said first, said third, said fifth and said seventh branches are connected to a first power-source-connecting terminal at a substantially constant potential,
the second terminals of said second, said fourth, said sixth and said eighth branches are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node, the second terminal of said fifth branch and the first terminal of said sixth branch are mutually connected at a third node, the second terminal of said seventh branch and the first terminal of said eighth branch are mutually connected at a fourth node,
three terminals of three loads in Y connection or xcex94 connection are connected to said first to third nodes, respectively,
said first branch includes a first output circuit for driving said loads,
said third branch includes a second output circuit for driving said loads,
said fifth branch includes a third output circuit for driving said loads,
each of said second, said fourth and said sixth branches includes a switch circuit, and
said seventh branch includes an auxiliary circuit for interlocking with one of said first to third output circuits and outputting an adjusting current adjusted to an amount smaller substantially by a predetermined ratio than an output current outputted from the interlocking output circuit in the case of applying substantially the same input voltage as that of the interlocking output circuit;
a potential difference detector for detecting the potential of said first node, said second node or said third node with respect to said fourth node;
a control circuit for making said first to third output circuits interlock with said auxiliary circuit in a predetermined order and controlling said first to third output circuits;
a switch control circuit for turning on or off one or two of said switch circuits in a predetermined order and combination in a manner synchronized with the operation of said control circuit; and
a current ratio compensator for feeding back said potential difference detected by said potential difference detector and for controlling the equivalent impedance across said first terminal and said second terminal of one of said first to said eighth branches, so that
a bridge consisting of said first branch, a composite of said loads and either or both of said fourth and said sixth branches, said seventh branch, and said eighth branch, keeps the balance when an output current from said first output circuit flows through said first branch, said loads, either or both of said fourth and said sixth branches,
a bridge consisting of said third branch, a composite of said loads and either or both of said second and said sixth branches, said seventh branch, and said eighth branch, keeps the balance when an output current from said second output circuit flows through said third branch, said loads, either or both of said second and said sixth branches, and
a bridge consisting of said fifth branch, a composite of said loads and either or both of said second and said fourth branches, said seventh branch, and said eighth branch, keeps the balance when an output current from said third output circuit flows through said fifth branch, said loads, either or both of said second and said fourth branches,
thereby holding said ratio at a substantially constant level.
The power control device can reverse the output currents flowing through the respective loads by turning on and off the respective output circuits and the switch circuits in a predetermined order and combination. That power control device is, for example, used as a driver for stator wire of three-phase synchronous motor or inductive motor. The arrangement of only the conducting branches of the output network is substantially the same as the bridge circuit of the above-described power control device and, therefore, the effects thereof are equivalent to the above-described one.
According to a preferred mode of the power control device from one aspect, said eighth branch includes a current setting circuit for holding at a substantially constant level or changing quasistatically said adjusting current. If the adjusting current is held constant with the current setting circuit, then the output current is constant, since the ratio of the output current to the adjusting current is held constant by the current ratio compensator. Alternatively, if the adjusting current changes quasistatically by the current setting circuit, then the output current also changes quasistatically in the same manner.
In the above-described power control device, preferably from yet another aspect, said current ratio compensator provides the control of said equivalent impedance over said switch circuits. Thereby, the switch circuit for reversing the current flowing through the load can also be used as a compensator for making the bridge circuit keep the balance.
According to a preferred mode of the above-described power control device from yet another aspect, said current ratio compensator may provide the control of said equivalent impedance over one of said first to third output circuits. Thereby, the same output circuit can be used in order to perform the original function as a driver for the load, the above-described function as a protective circuit against excess current and the function as the compensator for making the bridge circuit keep the balance.
A power control device according to the present invention developed into still another mode from the secondarily mentioned power control device according to the present invention, comprises:
an output network consisting of a first branch, a second branch, a third branch, a fourth branch, a fifth branch, a sixth branch, a seventh branch, an eighth branch, a ninth branch, a tenth branch, an eleventh branch and a twelfth branch, wherein
each of said first to twelfth branches includes a first terminal and a second terminal,
the first terminals of said first, said third, said fifth, said seventh, said ninth and said eleventh branches are connected to a first power-source-connecting terminal at a substantially constant potential,
the second terminals of said second, said fourth, said sixth, said eighth, said tenth and said twelfth branches are connected to a second power-source-connecting terminal at a substantially constant potential,
the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node, the second terminal of said fifth branch and the first terminal of said sixth branch are mutually connected at a third node, the second terminal of said seventh branch and the first terminal of said eighth branch are mutually connected at a fourth node, the second terminal of said ninth branch and the first terminal of said tenth branch are mutually connected at a fifth node, the second terminal of said eleventh branch and the first terminal of said twelfth branch are mutually connected at a sixth node,
three terminals of three loads in Y connection or xcex94 connection are connected to said first to third nodes, respectively,
said first branch includes a first output circuit for driving said loads,
said third branch includes a second output circuit for driving said loads,
said fifth branch includes a third output circuit for driving said loads,
each of said second, said fourth and said sixth branches includes a switch circuit,
said seventh branch includes a first auxiliary circuit for interlocking with said first output circuit and outputting a first adjusting current adjusted to an amount smaller substantially by a predetermined first ratio than a first output current outputted from said first output circuit in the case of applying substantially the same input voltage as that of said first output circuit,
said ninth branch includes a second auxiliary circuit for interlocking with said second output circuit and outputting a second adjusting current adjusted to an amount smaller substantially by a predetermined second ratio than a second output current outputted from said second output circuit in the case of applying substantially the same input voltage as that of said second output circuit, and
said eleventh branch includes a third auxiliary circuit for interlocking with said third output circuit and outputting a third adjusting current adjusted to an amount smaller substantially by a predetermined third ratio than a third output current outputted from said third output circuit in the case of applying substantially the same input voltage as that of said third output circuit;
a potential difference detector for detecting the potential of said first node with respect to said fourth node as a first potential difference, the potential of said second node with respect to said fifth node as a second potential difference and the potential of said third node with respect to said sixth node as a third potential difference;
a control circuit for operating in a predetermined order and controlling a pair of said first output circuit and said first auxiliary circuit, a pair of the second output circuit and said second auxiliary circuit and a pair of the third output circuit and said third auxiliary circuit;
a switch control circuit for turning on or off one or two of said switch circuits in a predetermined order and combination in a manner synchronized with the operation of said control circuit; and
a current ratio compensator for controlling the equivalent impedance across said first terminal and said second terminal of one of said first to twelfth branches,
for feeding back said first potential difference detected by said potential difference detector so that a bridge consisting of said first branch, a composite of said loads and either or both of said fourth and said sixth branches, said seventh branch, and said eighth branch, keeps the balance, thereby holding said first ratio at a substantially constant level when said first output current flows through said first branch, said loads, either or both of said fourth and said sixth branches,
for feeding back said second potential difference detected by said potential difference detector so that a bridge consisting of said third branch, a composite of said loads and either or both of said second and said sixth branches, said ninth branch, and said tenth branch, keeps the balance, thereby holding said second ratio at a substantially constant level when said second output current flows through said third branch, said loads, either or both of said second and said sixth branches, and
for feeding back said third potential difference detected by said potential difference detector so that a bridge consisting of said fifth branch, a composite of said loads and either or both of said second and said fourth branches, said eleventh branch, and said twelfth branch, keeps the balance, thereby holding said third ratio at a substantially constant level when said third output current flows through said fifth branch, said loads, either or both of said second and said fourth branches.
The power control device can reverse the output currents flowing through the respective loads by turning on or of f the respective output circuits and the switch circuits in a predetermined order and combination in the same way as described above. Therefore, the power control device can be used, for example, as a driver for stator wire of three-phase synchronous motor or inductive motor. The arrangement of only the conducting branches of the output network is substantially the same as the bridge circuit of the secondarily mentioned power control device according to the present invention and, therefore, the effects thereof are equivalent to the secondarily mentioned power control device.
The power control device, in contrast with the above-described power control device, has a plurality of the auxiliary circuits one-to-one corresponding to a plurality of the output circuits. Thereby, the circuit scale is larger than the above-described one. On the contrary, if the ratio of the adjusting current to the output current is set at a predetermined value with a high precision, the above-described power control device requires minimizing the structural difference among a plurality of the output circuits since the auxiliary circuit is used in common, but that power control device does not.
In addition, in the case of monolithically forming the power control device according to the present invention as an integrated circuit, the output circuits must be put apart from each other to a certain extent on the chip in the above-described power control device. Therefore, non-uniformity in position of the temperature or the wafer structure on the chip can easily appear as the difference between the operations of the plural output circuits and, as a result, the precision of the output control tends to drop. On the contrary, in that power control device, the output circuit and the auxiliary circuit, both of which correspond to each other, can be formed immediately next to each other and, therefore, the above-described non-uniformity of the temperature or the wafer structure can be substantially ignored for the pair of the circuits.
The power control device in a preferred mode according to one aspect has a current setting circuit in said eighth branch, said tenth branch and said twelfth branch each, for holding at a substantially constant level or changing quasistatically said first adjusting current, said second adjusting current and said third adjusting current, respectively. If the adjusting current is held constant with the current setting circuit, then the output current is also constant, since the ratio of the output current to the adjusting current is held constant by the current ratio compensator. Alternatively, if the adjusting current changes quasistatically with the current setting circuit, then the output current changes quasistatically in the same manner.
In the above-described power control device preferably from still another aspect, said current ratio compensator provides the control of said equivalent impedance over said switch circuit. Thereby, the switch circuit for reversing the current flowing through the load can also be used as the compensator for making the bridge circuit keep the balance.
In a preferred mode of the above-described power control device from yet another aspect, said current ratio compensator may provide the control of said equivalent impedance over one of said first to third output circuits. Thereby, the same output circuit can be used in order to perform the original function as a driver for the load, the above-described function as a protective circuit against excess current and the function as the compensator for making the bridge circuit keep the balance.
The above-described power control device according to the present invention is formed so as to include in the output network, two or three of substantially the same circuit parts as the bridge circuit of the secondarily mentioned power control device according to the present invention at the time of conducting the current during a predetermined period of the operation time. It would be easy for ordinary engineers who belong to a field related to the present invention (hereinafter referred to as those skilled in the art) to extend the power control device according to the present invention so as to make it include four or more of the same circuit parts, thereby use it as, for example, a four or more phase driver.
In addition, a power control device according to still another aspect of the present invention has at least two output control parts, each of which is the above-described power control device according to the present invention being able to reverse the current flowing through a load, and a micro-step control circuit for controlling said adjusting currents of said output control parts, thereby controlling the currents flowing through said respective loads.
That power control circuit can independently control the currents flowing through the respective loads included in the respective output control parts. That power control circuit is used as, for example, a driver such as in a stepping motor. Each of the output control parts has the same structure as the above-described power control device being able to reverse a current of a load and, therefore, the effects thereof are the same as the above-described power control device.
Each of the output control parts may have a current setting circuit for holding at a substantially constant level or changing quasistatically said adjusting current in the same way as the above-described power control device. The current setting circuit is included in a branch through which adjusting current from the auxiliary circuit flows. In addition, said current ratio compensator may provide the control of said equivalent impedance over said switch circuit or said output circuit. Owing to the above-described structure and effects, the output control with a high precision can be provided in the same way as the above-described power control device.
In the above-described power control device according to the present invention, preferably from one aspect, a main resistance in the periphery of said output circuit and an auxiliary resistance in the periphery of said auxiliary circuit interlocking with said output circuit are adapted to satisfy a substantial proportionality between said output current from said output circuit and said adjusting current from said auxiliary circuit. The main resistance is preferably connected in series with the output circuit and includes a parasitic resistance of the output circuit and a resistance which cannot be structurally removed. The auxiliary resistance is preferably connected in series with the auxiliary circuit. For example, as described above, in the case where the power control device according to the present invention has a bridge circuit consisting of four branches from the first to the fourth branches, the main resistance in the first branch is connected in series to the output circuit between the first and the second terminals of the first branch. An auxiliary resistance in the third branch is connected in series to the auxiliary circuit between the first and the second terminals of the third branch. Here, xe2x80x9cbeing adaptedxe2x80x9d means, concretely, that said auxiliary resistance has a resistance value substantially equal to the resistance value of said main resistance multiplied by the inverse of the proportional coefficient of said proportionality.
For example, in the case where the output circuit is formed as a semiconductor element, a resistance which cannot be structurally removed always exists in the periphery of the output circuit. Then, the auxiliary resistance having the above-described resistance value is arranged in the periphery of the auxiliary circuit. Thus, an error given by the main resistance to the ratio of the output circuit to the adjusting current can be reduced. Therefore, the precision of the output control can avoid reducing in spite of the existence of the main resistance.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better under stood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.